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This page will be devoted to giving
descriptions of new and untested ideas on LY Research &
Development.
Research workers are asked to suggest projects that
they would like to try - if only funding was available.
Planters
and home owners are asked to suggest ways of coming to terms with the
disease - if there are any.
Do not be put off by project
managers who don't like "science fiction" or pessimists
"who have tried it already."
Send your idea to
CICLY@yahoogroups.com
for general discussion
or directly to the Editor
with a request for it to be added to this page.
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Reinfection after natural remission?
Any palm can be infected with the LY phytoplasma(s) by the LY vector(s).
If the palm is from a susceptible variety the phytoplasma will usually kill it in a few months.
In some circumstances it may survive, without symptoms and without traceable phytoplasma, and it is presumed to have "escaped" infection.
We do not know any natural reason that might prevent a successful infection, but application of oxytetracycline hydorchloride (OTC) is one artificial reason.
Buf if the palm is from a resistant variety we assume that infection hasn't occurred
What if there is a natural equivalent of OTC in resistant palms that prevents the phytoplasma from killing the plant but doesn't eliminate it either (we could call it COC-O-TC)?
If anything interfers with the action of this COCOTC the phytoplasma may become active, and resistance may be overcome.
Taking the potato as an anology (but not as a strict botanical comparison) does a phytoplasma infection at one sprouted "eye" reach another sprout or does OTC applied to one such sprout protect the other eyes? Does an infected tuber carry phytoplasma into the next growing season?
Think of the palm trunk as the potato tuber.
After infection either OTC or its natural equivalent may control the phytoplasma - presumably by reducing the amount of phytoplasma in the palm tissue.
Much of that tissue is lost (leaves fall or roots stop growing) and may be replaced by healthy tissue (new leaves and new root growth)
I suggest that in some circumstances the infected tissues are all lost and that the healthy palm might then be free from phytoplasma.
Or does the stem represent "storage" of phytoplasma? As the potato tuber might?
Would reinfection years later re-awaken dormant phytoplasma in stem tissue?
From: http://groups.yahoo.com/group/CICLY/message/1079
Comments please, to the editor.
Suggestion for LY vector screening:
From active LY epidemic areas collect insects by non-destructive methods (i.e. not by sticky trap)
Attract with coloured light to motorised suction pump that drops insects into a chamber that is kept at ambient shade temperature by the air movement. With modern battery operated equipment this could be done at ground level or at the height of the palm canopy.
At (hourly/daily/weekly/appropriate, regular/frequent) intervals the trapped insects are removed to the laboratory and washed using a solution that will deactivate surface phytoplasma without causing the insect to be squashed, burst or otherwise release or regurgitate any internal phytoplasm (Does such a liquid exist? Or does it have to be developed?)
Sort insects mechanically / automatically into size and colour grades (and any other possible categories). Equipment was developed for counting aphis at Rothamsted 30 years ago so something better must be available by now.
Keep a small sub-sample of each size/colour category (store in liquid N?)
Remainder of sample used for DNA testing (What is the minimum amount needed? It might be necessary to split big samples or bulk small ones. Any bulking would be done with the same size/colour category from previous or successive trappings)
The whole idea depends on the DNA technique. All we need to be able to show is the presence, or absence, of LY. We do not, at this stage, need to identify a particular insect. Will there be a stronger signal if many insects in the sample are carrying LY? Will other (non-LY) phytoplasma in other (non-vector) insects cause any misreading of signals?
The following results
might be anticipated:
(a) all samples are always positive -
contamination
(b) no samples are ever positive - wrong
techniques
(c) some samples are sometimes positive/negative -
might indicate seasonality
(d) some samples are always negative -
might indicate what genera or species to ignore
(e) some samples
are always positive - may indicate an effective year round vector
Over a period of time it might be possible to show that the absence of positive results at certain periods (dry season, heavy rain periods etc) could indicate seasonality and possibly save manpower by eliminating collection (for cage testing) at times when infective vectors are scarce or absent.
In contrast, a high seasonal count of positive results would indicate the best times for such collecting.
Possibly an absence of positive results in the smallest size categories might indicates that entire groups of small insects (eg Empoasca?) could be ignored in future.
Likewise if one colour category never shows a positive results that may also allow a particular species to be ignored.
Likewise the absence of positive results from the larger size categories could elimainate other insect groups.
If a phytoplasma infected vector is present then positive results would be anticipated from two or three contiguous categories (to allow for natural variation in size or colour).
A wide range of size categories might indicate that one vector is infective whether young (small), mature (larger) to old (largest)
Two contasting groups (very small green / very big brown) with no intermediate groups might indicate more than one vector.
Depending on which of the above results appear, the stored sub-samples could then be investigated.
At this stage a taxonomist would be needed to show which insect (group) consistently turns up in positive samples.
Individual insects from these sub-samples might be tested for presence of LY phytoplasma.
Finally, cage tests could be carried out using the candidate insect selected by this method and collected at the best time of year as indicated by this method.
From: http://groups.yahoo.com/group/CICLY/message/941
Comments please, to the editor.
Sugar cane and coconut palm phytoplasmas
The phytoplasmas in sugarcane seldom reach high titres, and the host plant itself, with the numerous complex polysaccharides generated naturally, as well as the phenolic and tannic compounds generated during disease conditions, makes it one of the more difficult plants to detect phytoplasmas in effectively. As is often the case, the observations in sugarcane were found to be repeated in phytoplasma-like diseases in other host plants, and I have learned a lot from the study of the coconut diseases that helped to put what we observe in sugarcane into perspective. I would venture a guess that we would eventually find a close link between a number of these diseases, as well as an "alternate host" situation. The link is also not altogether surprising, since in quite a number of subsistence farming situations, coconuts and sugarcane is grown in close proximity.
Comments please, to the editor.
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Vectors
I recently had the opportunity to be involved in some peripheral research on a problem related to sugarcane in Jamaica, and although the phytoplasma found in a limited number of samples was not associated directly with the sugarcane problem, it is interesting to note that this phytoplasma was in the Pigeon Pea witches broom group, which in turn, is a close relation of LY. It is also of interest that Myndus is also known as the " yellow sugarcane leafhopper "(Pers. comm, Nigel Harrison). Such a "link" would be extremely interesting to follow up.
Comments please, to the editor.
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Resistance
One other point of interest is the varying reaction of LY "resistant" coconut types in other geographical regions outside of the Carribean. It has now been established (two recent papers by Tymon et.al) that the African diseases represent at least two new types, and my research on the classification of these "coconut" phytoplasmas has shown that they are probably more distantly related to the LY type than was reported initially. The newly discovered phytoplasmas from Indonesia fall in an even more distantly related group. This variation in the phytoplasmas involved could partially, in addition to geographical location effects, explain the variation in tolerance of supposedly "resistant" coconut cultivars.
Comments please, to the editor.
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Africa
As far as LY or LY-like symptoms in our local palms (South African) are concerned, I am sure that phytoplasmas occur in this part of the world, but probably not the Carribean LY. It is also true that we are not a coconut producing area, and this crop is not considered to be a viable agricultural crop for this part of the world. There has been a confirmed report of the west African phytoplasma in coconuts grown in Mozambique, basically just up the road from us. Unfortunately, because of the high cost of biotechnology based research, we cannot conduct surveys at random, and would only do so if we can obtain funding from interested parties. There has been some contact with researchers in the rest of Africa relating to phytoplasma diseases, but not nearly at the level that it could be called "useful" up to now.
Comments please, to the editor.
One aspect that intrigues me, and that I would like to "test the waters" in this group is the possibility of seed transmission of the phytoplasmas in coconuts. This would be an "elegant" answer to how these phytoplasmas have managed to spread around, and could also explain some of the "unanswered" occurrence of the phytoplasmas in very remote areas. Are we undeservedly and categorically and undeniably certain that this does not happen?
Comments please, to the editor.
International
survey of coconut phytoplasmas
The case of the African coconut phytoplasmas, Natuna/Kalimantan, Root wilt disease in India and some samples I have seen from Belize show that a thorough international survey of the phytoplasmas involved with coconuts is overdue. The new molecular techniques enable us to do such a survey, but is costly. It is obvious that there is more than one phytoplasma involved with coconut diseases globally, and this has far-reaching implications for trade in coconuts, especially of live material intended for propagation, as well as for sustainable production in newly developed areas. Do we wait for these disease to run their course, or do we find out as much as possible about them before they cause too much damage to already tenuous productivity?
Comments please, to the editor.
Back in the late 70s I looked at a coconut disease in
North Sumatra and Malaysia that Peter Turner and Ray Kenten had
called Coconut Stem Necrosis. After a lot of EM studies for viruses
and phytoplasmas I found bodies that looked like phytoplasmas. The
work was published in
the Perak Planters Journal. No antibiotic
studies were done and molecular methods were not
available. If I
was doing the work today I would want molecular and/or antibiotic
studies to confirm aetiology.
I still have the EM blocks and
am wondering if it might be possible to extract DNA from these for
PCR studies. This sort of study would open up a whole vault of
speciments from other suspected phytoplasma diseases that could be
tested. If anyone is willing to fund a project I'd like to hear from
them.
Comments please, to the editor.
There is a suggestion that CICLY could be a good
place for anyone seeking advice on an LY problem to get in touch with
the right specialist. The idea came from someone who was recently
contacted about a consultancy that was a little out of his line.
Rather than passing a message around between colleagues, he suggests
that if a CICLY member gets a request that they cannot personally
fulfil, he or she could forward it to CICLY who would forward it to
the most appropriate candidates. In addition, CICLY could organise an
informal team and ask other experts to work with whoever becomes the
consultant.
Without trespassing on the interests of commercial
consulting agencies, could CICLY could play a role in situations in
which someone would like to locate the most qualified person for some
particular task related to LY?
Comments please, to the editor.
The concept of LY Disease Resistance Ranking, based on trials, field observations and theory, is offered for discussion:
Rank 1 - highest resistance - Dwarf Domestic Type - Malayan Dwarf (MD)
Rank 2 - high resistance - Dwarf x Tall (DxT) Hybrids between Rank 1 x Rank 3 - Maypan
Rank 3 - intermediate resistance - Tall Domestic Type - American Pacific Coast Tall - also some DxT hybrids (Rank 1 x Rank 5) Mayjam and PB121
Rank 4 - low resistance - Introgressed Tall Type - most Southeast Asian & Pacific Island Tall varieties (hybrid between rank 3 and Rank 5)
Rank 5 - no resistance - Tall Wild Type - American & African Atlantic Coast Tall types - Jamaica Tall, West African Tall etc.
The ranks are not distinctly independent (they merge and overlap) and the actual level of resistance susceptibility will be strongly influenced by growing conditions, vector populations etc,
The possibility exists for subdivisions between the ranks:
Rank 1.5 - backcross between MD and Maypan
Rank 2.5 - hybrids betweeen MD and Asian or Pacific varieties, perhaps Maren
Rank 3.5 - introgressed sub-population where rank 3 predominates (perhaps the Rennell Tall) or populations produced by crossing Maypan and Jamaica Tall
Rank 4.5 - introgressed sub-population where rank 5 predominates (perhaps the East African Tall) or hybrids between WAT and Pacific or Asian Tall types.
Comments please, to Hugh Harries or to the editor.
This page is under continuous review. If you have an idea or an opinion to improve the contents of the page or the site, tell the editor. If you disagree with anything, say so. If you don't see or get a satisfactory response in a reasonable time contact other participants. At all time keep in contact with other individuals; this site is not a substitute for person to person contact.